WASHINGTON — Drone advocates urged the Federal Aviation Administration at a Senate hearing Wednesday to allow the aircraft into general airspace faster because countries such as Japan are friendlier to the innovative technology.

Some members of the Senate Commerce, Science and Transportation Committee voiced concern about maintaining drone safety and protecting privacy as more drones fill the skies.

"Lives are at stake," said Sen. Jay Rockefeller, D-W.Va., the panel chairman. "One of the most important problems the FAA and the industry are trying to solve is avoiding collisions between unmanned and piloted aircraft."

There is a sense of urgency to the testing and development of regulations. Congress set a September 2015 deadline for the FAA to regulate sharing the skies between drones and commercial airliners.

FAA Administrator Michael Huerta said the agency must set standards for safely operating drones, making sure they avoid other aircraft and ensuring they land safely if they lose connection with the remote pilot.

"There will be challenges to this integration," Huerta said.

He released a road map for the industry in November and named six test groups in December. The FAA anticipates 7,500 drones in the skies within five years, if regulations allow. Huerta said regulations will be prioritized and phased in.

"We must meet these obligations in a thoughtful and careful manner," Huerta said.

Missy Cummings, a former Navy fight pilot who is director of the humans and autonomy lab at Duke University, doubted the FAA would meet the 2015 deadline.

"While we are making some progress towards this goal, the United States is lagging, not leading, the commercial drone boom," she said.

Manufacturers are impatient.

Yamaha Motor's RMAX drone has been fertilizing crops in Japan for 20 years and more recently in Australia and South Korea, according to Henio Arcangeli, vice president for new business development. Drones fertilize a part of Japan equal in size to Delaware and Rhode Island combined, he said.

At 140 pounds and 9 feet long, the $100,000 remote-piloted helicopter is larger than hand-held hobbyist aircraft that could win earlier federal approval.

Trained pilots keep an eye on the drone during daylight hours, Arcangeli said. The drones can fertilize 11 acres of vineyards in Napa Valley in the time it takes a tractor to cover 1 acre, he said.

"There is no reason to delay all commercial (drone) use for the several years it will take the FAA to develop more comprehensive regulations," Arcangeli said.

Rockefeller and Republican Sen. Dean Heller of Nevada, one of the six testing locations, asked why the FAA is 20 years behind other countries in developing drone regulations.

"Why are we not at the forefront of the world?" Heller asked.

Huerta said U.S. airspace is much more complicated than Japan's because of many more general-aviation planes. Drone technology has grown quickly and unpredictably, he said.

"Even today, we don't have a complete understanding of where this might go in the future," Huerta said.